1. Technical Field
The present invention relates to a vehicle seat that is equipped with a side airbag device.
2. Related Art
A seat structure that is equipped with an airbag device for a side collision is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 9-76859. In this structure, a substantially U-shaped slit is formed, with the seat rear side remaining, in a region of a side framing portion of a seat pad which region faces the outer peripheral portion of a side airbag. The region at the inner side of this slit is a cover portion for an airbag case, and opens toward the seat outer side at the time when the side airbag inflates and expands.
An airbag device for a side collision is disposed in JP-A No. 9-254735. In this device, a sewn portion (a burst line portion), that ruptures due to the expansion pressure of a side airbag is provided in a surface material of the backrest portion of a seat (in the seatback skin), in a vicinity of the opening portion of an airbag case. Further, a seatback pad of a predetermined thickness is interposed between the seatback skin and the airbag case. A slit portion, that is rectilinear or is substantially U-shaped and through which the side airbag is inserted at the time of expansion, is formed in this seatback pad at the inner side of the burst line portion.
Among side airbags such as those described above, there are those that are large-sized and restrain a region that includes not only the chest portion of a vehicle occupant, but the shoulder portion as well. For example, there are side airbags that restrain the region from the lumbar portion to the shoulder portion of a vehicle occupant, and there are side airbags that restrain the region from the abdominal portion to the head portion of a vehicle occupant. There are cases in which it is difficult to inflate and expand such large-sized side airbags stably in the intended direction or at the intended position with respect to the vehicle occupant. The tendency for the expanding direction of a side airbag to become unstable is marked particularly in cases in which the sewing line of the seatback skin that structures the burst line portion is set in a complex shape.